The rate and rhythm of the heart are controlled by a small collection of specialized nervous tissue known as the sinuatrial node, situated at the base of the heart. This is the natural pacemaker of the heart-or cardiac pacemaker. When the impulse sent out by this pacemaker cannot reach all parts of the heart (a condition known as heart-block), the heart either stops or contracts in an irregular manner.
In these cases, the natural pacemaker can be replaced by an artificial pacemaker which, for all practical purposes, is a battery which stimulates the heart and allows it to beat at normal speeds. The pacemaker generates controlled, periodic, direct electric potentials (pulse voltages) through electrodes buried in a patient's chest (reaching the heart area). Thousands of encapsulated, implantable pacemakers are in use throughout the nation today. In addition, temporary externally-worn pacemakers are in use which are either fixed to the outside of the chest or upper or lower extremity and connected to an electrode catheter which is passed through a vein into the appropriate heart chamber.
Problems often arise in respect to the placement and anchoring of the pacemaker electrodes. Unless the electrode is properly anchored during initial insertion, it can pull out of the heart tissue. Obviously, if it does so, the heart can no longer be stimulated by the pacemaker. The result is cardiac arrythmia or cardiac arrest, or emergence of the underlying rhythm because of pacemaker malfunction.
As shown in FIG. 1, prior art electrodes are provided with barbs to facilitate insertion of the probe into the heart tissue. The barbs are provided with openings through which heart tissue can grow once the electrodes are in place to thereby anchor the electrode. The main drawback of the prior art electrodes is that it takes a considerable amount of time for new heart tissue to grow around the electrode and through the opening of the barbs to permanently anchor the electrode in place. Until a sufficient amount of tissue has grown through the openings, the electrode can easily become dislodged.
The present invention prevents the electrode from becoming dislodged during initial insertion. A barb traps the trabeculae in the heart acutely during initial insertion and thereby holds the electrode firmly in place until sufficient heart tissue has grown around the electrode to anchor it permanently.